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Mixed ion–electron conductors have a wide range of important applications in devices relying on mixed ion–electron transport, mainly including conducting polymer composites and ceramics. Herein, we...

Zero/negative thermal expansion (ZTE/NTE) materials are significantly desired in many applications; however, it is still a tremendous challenge to theoretically predict and successfully achieve new families of ZTE/NTE materials via rational structural designs. Herein, we present a new low-thermal expansion/NTE material, i.e. a lamellar vanadium oxide hybrid [C3H12N2][V4O10] consisting of mixed-valence {V4O102−}∞ monolayers and propane-1,3-diammonium cations in the interlayers. The inorganic layer is parallel to the (001) plane and comprises edge-sharing VO5 square pyramids linked together via corner-sharing VO4 tetrahedra. The hybrid shows a low thermal expansion coefficient (∼10−6 K−1) in the wide temperature range of 90–250 K and a colossal NTE (∼−600 × 10−6 K−1) between 293 and 330 K. Moreover, a reversible thermal anomaly occurs at ∼328/316 K upon heating/cooling, associated with a structural phase transition, which gives rise to switchable dielectric and ion-conducting properties; this study provides a new method for the exploration of lamellar vanadium oxide hybrids as new low-thermal expansion/NTE, switchable dielectric and ion-conducting multifunctional materials.

As a class of anionic oxoclusters of early transition metals in their highest oxidation states, polyoxometalates (POMs) show considerable structural versatility and unique chemical and physical properties, making them promising multifunctional materials. In this study, a Keggin-type POM has been achieved, with a formula of [(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O (1), and its microcrystals and nanocrystals have been obtained, respectively. This POM was characterized by elemental analysis for C, H and N, ICP-MS, TG, PXRD, SEM, X-band EPR and XPS techniques. Single crystal X-ray diffraction analysis demonstrated that 1 shows a rare extended structure with a high-connected three-dimensional (3D) all inorganic network of a Keggin-type POM, built from {Mo4.55V7.45PO40}10.45− polyoxoanions and {(H2O)0.3@K6(H2O)12}6+ clusters with CsCl-type crystal structure. In addition, to the best of our knowledge, 1 shows the highest ratio of vanadium to molybdenum among Keggin-type POMs reported thus far. Most interestingly, 1 exhibits intrinsic proton conduction below the freezing point of water, with a proton conductivity of 6.90 × 10−7 S cm−1 at 249 K and further reaching 3.36 × 10−6 S cm−1 at 272 K and Ea = 0.44 eV at 249–272 K.

The emerging organic ion plastic crystals (OIPCs) are the most promising candidates used as solid-state electrolytes in a range of ionic devices. To endow an OIPC with additional functionality may create a new type of material for multifunctional devices. Herein, we present an ion plastic crystal, [EMIm]­[Ni­(mnt)2] (1; [EMIm]+ = 1-ethyl-3-methylimidazolium and mnt2– = maleonitriledithiolate), and its crystal consists of twin dimeric chains of [Ni­(mnt)2]− anions, embraced by [EMIm]+ cations. A crystal-to-plastic crystal transformation with a large latent heat that occurred at ∼367/337 K on heating/cooling is confirmed by the differential scanning calorimetry (DSC) technique. The plastic crystal phase in 1, characterized by variable temperature powder X-ray diffraction (PXRD) and optical microscopy images, spans a broad temperature range with ΔT ∼123/153 K on heating/cooling (DSC measurement), and the wide ΔT is relevant to an extra stable anion chain owing to the strong antiferromagnetic (AFM) interactions protecting the chain from collapse in the plastic crystal state. 1 is a single-component ion plastic crystal with a record high ion conductivity, 0.21 S·cm–1, at 453 K. The crystal-to-plastic crystal transformation in 1 is coupled to a bistable magnetic transition to give a multi-in-one multifunctional material. This study provides a creative thought for the design of OIPCs with striking thermal, electrical, and magnetic multifunctionality.

Haloplumbate-based perovskites display promising functionalities for advanced photovoltaic, optoelectronic and other applications with high performances and low costs. Herein, we present a study of variable-temperature crystal structures, dielectrics and conductance at 153-513 K, and luminescence at ambient temperature for a one-dimensional organic-inorganic perovskite, [N-methyldabconium]PbI3 (1). Hybrid 1 shows extra thermo- and water-stability (thermal decomposition at ca. 653 K), switchable dielectric behaviour and conductance at around 348 K, owing to symmetry-breaking structure phase transition from the hexagonal space group P63/mmc in the high-temperature phase to the orthogonal space group Pcba in the low-temperature phase, and bright yellow-green emission at room temperature, originating from the electron transition within the semiconducting {PbI3}∞ chains. This study will broaden the scope of lead halide-based hybrid materials for practical application in optical and electrical devices.

In this study, two isomorphic hybrid crystals of iodoargentate, M(en)3Ag2I4 (M = transition metal Mn2+ (1) or main-group metal Mg2+ (2) ion), have been prepared through in situ self-assembly in DMF solution at ambient temperature and characterized by microanalysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction and single crystal X-ray diffraction techniques. The magnetic properties of 1 have been investigated. The crystals of 1 and 2 crystallize in the hexagonal non-centrosymmetric space group P6322 with rather similar lattice parameters. The metal complex M(en)32+ (M = Mn2+ or Mg2+) with the symmetry of D3 point group plays a crucial role in directing the formation of the three-dimensional hexagonal non-centrosymmetric framework of {Ag2I42−}∞. To the best of our knowledge, the hybrid Mg(en)3Ag2I4 is the first example of a main-group metal complex used as a structure directing agent for the formation of a hybrid crystal structure, and this is also the first instance where isomorphic hybrid crystals are obtained using transition and main-group metal complexes. These findings can provide a basis for broadening the utilization of metal coordination cations/anions as structure directing agents in the design and construction of novel hybrid crystal structures in more effective ways.

A supramolecular crystal, built from a 1 : 1 molar ratio of potassium tetraphenylboron (KBPh4) with 1,4,7,10,13,16-hexaoxacyclooctadecane (18-Crown-6), contains an organometallic half-sandwich superstructure unit {K(18-Crown-6)(ηn-C6H5B(C6H5)3)} (1 with n = 1–6), and shows a reversible phase transition at ∼211 K. The analysis of crystal structures at 173 K in the low-temperature phase, and 293 and 423 K in the high-temperature phase revealed that the breaking-symmetry phase transition is associated with the order–disorder transformation of [K(18-Crown-6)]+ and the change of the coordination mode of the phenyl ring to K+. A dielectric anomaly appears at ca. 212 K and dielectric relaxation occurs above 375 K in 1. The dielectric and thermal anomaly temperatures are close to each other, and the dielectric relaxation is relevant to the relative displacement of [K(18-Crown-6)]+ and the tetraphenylboron anion.

Owing to its outstanding water-retention ability, viscoelasticity, biocompatibility and non-immunogenicity, Hyaluronic acid (HA), a natural linear polymer alternating linked by d-glucuronic acid and N-acetylglucosamine, has been widely employed in cosmetic, medical and clinical applications. With the development of synthetic biology and bioprocessing optimization, HA production via microbial fermentation is an economical and sustainable alternative over traditional animal extraction methods. Indeed, recently Streptococci and other recombinant systems for HA synthesis has received increasing interests due to its technical advantages. This review summarizes the production of HA by microorganisms and demonstrates its synthesis mechanism, focusing on the current status in various production systems, as well as common synthetic biology strategies include driving more carbon flux into HA biosynthesis and regulating the molecular weight (MW), and finally discusses the major challenges and prospects.

The synthesis and physico-chemical characterization of an organic-inorganic hybrid material, (N, N'-bi-n-butyl-4,4′-bipyridinium tetrabromocuprate, has been reported. This hybrid has been characterized using IR, thermogravimetric and single-crystal X-ray diffraction analyses. In the title salt, (C18H26N2)[CuBr4], the CuBr42 − ion shows distorted tetrahedral geometry. The tetrabromocuprate and N, N'-bi-n-butyl-4,4′-bipyridiniums are held together via non-classical C H ⋯ Br hydrogen bond to form a 3-D hybrid structure. The percentages of hydrogen bonding interactions are analyzed by fingerprint plots of Hirshfeld surface. The XPS spectrum exhibits the signals of coexistence of CuI and CuII ions. However, the hybrid shows EPR silent behavior at room temperature and variable-temperature magnetic susceptibility displays an isolation of CuII feature with C = 0.46 emu K mol− 1 and θ approximate to − 0.06 K in 2– K as well. Such a novel nature is further analyzed and discussed.

A bimetallic metal–organic framework (MOF) with the formula [Zn3btc2{Cr3O(isonic)6(H2O)2(OH)}]·(DMF)15.5(H2O)8 (H3btc=1,3,5-benzenetricarboxylic acid; isonic=isonicotinicate) shows a pillar-layered structure. The monolayer consists of hexagon-like rings formed by the [Zn(isonic)2(btc)2] tetrahedral and the consecutive monolayers are pillared by trigonal–prismatic clusters of [Cr3O(isonic)6(H2O)2(OH)]through the remaining binding sites of the Zn2+ ions. DMF and water molecules are confined in the cages and channels. TGA indicates that the lattice DMF and water molecules begin to be released at temperatures above 363 K. Dielectric measurements were carried out in the range of 173–363 K and 1–107 Hz for three successive thermal cycles. The dielectric spectroscopy obtained in the first thermal cycle was different from that observed in the next two thermal cycles, while the dielectric spectra in the last two thermal cycles were almost identical. The dielectric nature of this MOF is discussed in detail for each thermal cycle. Since MOFs are unique host–guest systems in which the structure of the host framework is designable and the guests are exchangeable, it is no doubt those MOFs are materials with a variety of dielectric natures. This study gives a fresh impetus to achieve MOFs–based dielectric materials.

The solid state electrolytes show a wide range of practical applications in a variety of all-solid-state electrochemical devices, and it is highly in demand to explore new types of solid state electrolyte materials. In this study, we have designed and prepared a fluorite-type coordination compound, [Mn(en)3]I2, which has been characterized by microanalysis for C, H and N elements, infrared spectrum in the wavenumber range of 4000–400 cm−1, thermogravimetric analysis and differential scanning calorimetry. The single crystal X-ray diffraction revealed that the bigger size [Mn(en)3]2+ cations build three-dimensional network in the crystal of [Mn(en)3]I2 and the smaller size iodide ions occupy the tetrahedral or octahedral cavities surrounded by the [Mn(en)3]2+ cations, featuring as the fluorite-type compound. The impedance spectra were investigated to reveal the ionic conductivity σ = 3.45 × 10−11 S cm−1 at 303 K, while σ = 1.37 × 10−6 S cm−1 at 423 K, sharply increasing by five orders of magnitude regarding to that at 303 K. The electric modulus analysis further confirmed the conductance contributed from the migration of iodide ions. This study opens a way to design and achieve new coordination compound-based ion conductors.